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[Bug rtl-optimization/42889] [4.5 Regression] "-fcompare-debug failure (length)" with "-O1 -fgcse"
- From: "steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 28 Jan 2010 16:28:03 -0000
- Subject: [Bug rtl-optimization/42889] [4.5 Regression] "-fcompare-debug failure (length)" with "-O1 -fgcse"
- References: <bug-42889-14164@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #14 from steven at gcc dot gnu dot org 2010-01-28 16:28 -------
Re. comment #12: I think both: Do not call df_set_bb_dirty in df_insn_rescan
rescans a DEBUG_INSN, *and* mark dirty only certain problems. The last part is
probably the most tricky bit: which problems to mark. I think the RD and CHAINS
problems, at least, still need updating.
Updating a DF problem doesn't have to be a problem if the update doesn't result
in any code changes. The fact that we run DCE in an LR update is a Bad Thing
that was an unfortunate but necessary hack to fix some PR or another. But in
general the DF problems shouldn't do any code modifications.
I guess it should be documented somewhere that all DF problems except LR should
not even think about modifying any insns...
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42889